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Trigger Pull Up
E8491B
Outp ut Trig g er State LH = N orm ally Low , Hig h True
Outp ut Trig g er State HL = N orm ally Hig h, Low True (Default)
Figure 3-2. Using a Pull Up on the HP E8491B 'Trig Out' Port.
Using HP E8491B
Shared Memory
Locating E8491B Shared
Memory
Chapter 3
Trigger signals output from the E8491B 'Trig Out' port can be "pulled up"
to +30V as shown in Figure 3-2.
" TRIG OUT "
SM B Connec tor
The E8491B has 128 kBytes of shared (VME) memory. This memory is in
the E8491B's A24 address space and is available to those VXI instruments
capable of mapping and accessing A24 memory. Shared memory is often
used as a temporary storage space for data transfers between the PC and VXI
instruments.
HP instruments with the ability to store and receive data from shared
memory generally implement the SCPI (Standard Commands for
Programmable Instruments) MEMory:VME subsystem shown below:
MEMory:VME:SIZE
MEMory:VME:ADDRess
MEMory:VME:STATe
Corresponding HP VXIplug&play functions are:
hpexxxx_memVmeAddr
hpexxxx_memVmeSize
hpexxxx_memVmeStat
where xxxx is the instrument model number.
In order to use the E8491B shared memory, you must first locate the starting
address of the memory as mapped by the resource manager (see "Running
the Resource Manager" in Chapter 2). The address varies from system to
system depending on the number of devices that use A24 memory. The
address can be determined programatically using HP VISA or SICL, or by
viewing the resource manager output. Each method is described in the
following sections.
+ V = Pull Up Voltag e (+ 30V M ax)
+ V
R
VXI Programming Using the IEEE 1394 Serial Bus
DUT
47
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